The present invention relates generally to controlling the exhaust temperature of spark ignition engines operating with a cold start and spark retard and enleanment methodology and more particularly, to a method for generating additional engine load using existing vehicle systems during periods of engine cold-start and warm-up.
Stringent standards have been placed on emissions for internal combustion engines for cars, trucks and other vehicles to control the amount of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) that are released into the atmosphere. However, increasingly more stringent emissions standards are being placed on vehicles, and still further emissions reductions for engine operation are being implemented.
A considerable amount of total emissions occur during engine warm-up. During this time period, the emissions-reducing catalysts located in the catalytic converters are largely ineffective due to the fact that they have not reached a temperature at which significant catalytic activity can be maintained, also known as light-off. Thus attempts have been made to decrease emissions during engine warm-up by decreasing the time it takes to raise the exhaust temperature to light-off.
Cold start spark retard and enleanment (CSSRE) is a process used to decrease cold-start emissions. With CSSRE, hydrocarbons are oxidized prior to exiting the exhaust system and the catalyst is rapidly heated by high exhaust temperatures. During a cold start with CSSRE, engines operate at 1200 RPM, 1 bar brake mean effective pressure (BMEP), slightly lean air/fuel ratios and heavily retarded spark timing. While CSSRE enables engines to meet stringent emissions standards, it subjects the engine to extremely retarded spark timing and lean operating conditions, thereby increasing cycle-to-cycle variations, which adversely affects the engine""s stability and increases the requirements for the fuel delivery systems and engine controls for air/fuel mixtures and spark timing.
There is a need for fast and robust catalyst light-off during engine cold-start and warm-up periods in order to speed-up catalyst light-off and meet stringent emissions standards. Therefore there is a need for improved CSSRE methods that improve engine performance and reduce emissions.
It is an object of the present invention to introduce an auxiliary load on an engine operating with CSSRE during periods of engine idle to produce higher exhaust gas temperatures for rapid catalyst light-off.
In carrying out the above objects and other objects and features of the present invention, a system and method is provided for increasing the load of an engine during idle conditions in order to speed-up catalyst light-off for a high load cold start and spark retard and enleanment methodology. The engine is operating with a CSSRE method.
It is preferred to operate the engine while additional auxiliary loads are placed on it. According to the present invention, additional loads are generated by existing systems on the vehicle. For example, in one embodiment a compressor generates the additional loads in the air-conditioning system. In the alternative, the additional loads may be generated by a starter/alternator. The present invention is advantageous in that it provides a high-load CSSRE method, which functions without additional hardware components, complexity or cost. The present invention requires some software changes in order to control an electronic engine control module.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.